Effect of the Molecular Weight on the Whole Conformation of a Liquid Crystalline Comb-like Polymer in Its Melt

Fourmaux-Demange, V.; Boué, François; Brûlet, Annie; Keller, Patrick; Cotton, J. P.

doi:10.1021/ma9712864

Cited by 19 publications

(30 citation statements)

References 21 publications

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“…Therefore, it seems that the orientation of the mesogens is produced by a relaxation in the sample. For all the samples, the S values are smaller than those obtained by orientation in a magnetic field [17] (0.55 < S < 0.7).…”

Section: Orientation Of the Mesogenic Corescontrasting

confidence: 61%

“…We performed a first series of neutron scattering experiments on non-deformed samples [17]. They showed that, in the isotropic phase, the backbones of PMA-CH 3 and PMA-MCH 3 (its isomeric form) had the same conformation as that of a usual linear flexible polymer, such as polystyrene.…”

Section: Polymers: Synthesis and Characterizationmentioning

confidence: 99%

“…smectic ordering can be observed but only at a short range. The chains remain Gaussian perpendicular to the director but escape occasionally from the confinement brought about by the smectic fluctuations [17,18]. For PMA-CH 3 , the viscosities (η 0 ) and terminal times (τ ter ) have been previously determined [5].…”

Section: Polymers: Synthesis and Characterizationmentioning

confidence: 99%

“…R g is the radius of gyration of the non-deformed chain [17]. The inertial radii R and R ⊥ are measured in the Guinier range according to…”

Section: Orientation and Chain Conformation 41 Analysis Of The Form mentioning

confidence: 99%

“…We could be tempted to apply it to CL polymers since their chain conformation at rest is Gaussian [17], with as much flexibility as polystyrene. Actually, oscillatory shear experiments in the isotropic phase show that most of the comb-like polymethacrylate chains studied were not entangled [9], at least with the classical vision of entanglements [5].…”

Section: The Cluster Questionmentioning

confidence: 99%

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Influence of the nematic order on the rheology and conformation of stretched comb-like liquid crystalline polymers

et al. 2000

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We have studied the rheology and the conformation of stretched comb-like liquid-crystalline polymers. Both the influence of the comb-like structure and the specific effect of the nematic interaction on the dynamics are investigated. For this purpose, two isomers of a comb-like polymetacrylate polymer, of well-defined molecular weights, were synthesized: one displays a nematic phase over a wide range of temperature, the other one has only an isotropic phase. Even with high degrees of polymerization N , between 40 and 1000, the polymer chains studied were not entangled. The stress-strain curves during the stretching and relaxation processes show differences between the isotropic and nematic comb-like polymers. They suggest that, in the nematic phase, the chain dynamics is more cooperative than for a usual linear polymer. Small-angle neutron scattering has been used in order to determine the evolution of the chain conformation after stretching, as a function of the duration of relaxation t r. The conformation can be described with two parameters only: λp, the global deformation of the polymer chain, and p, the number of statistical units of locally relaxed sub-chains. For the comb-like polymer, the chain deformation is pseudo-affine: λp is always smaller than λ (the deformation ratio of the whole sample). In the isotropic phase, λp has a constant value, while p increases as tr. This latter behavior is not that expected for non-entangled chains, in which p varies as tr 1/2 (Rouse model). In the nematic phase, λp decreases as a stretched exponential function of tr, while p remains constant. The dynamics of the comb-like polymers is discussed in terms of living clusters from which junctions are produced by interactions between side chains. The nematic interaction increases the lifetime of these junctions and, strikingly, the relaxation is the same at all scales of the whole polymer chain.

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Section: Orientation Of the Mesogenic Corescontrasting

confidence: 61%

Section: Polymers: Synthesis and Characterizationmentioning

confidence: 99%

Section: Polymers: Synthesis and Characterizationmentioning

confidence: 99%

“…R g is the radius of gyration of the non-deformed chain [17]. The inertial radii R and R ⊥ are measured in the Guinier range according to…”

Section: Orientation and Chain Conformation 41 Analysis Of The Form mentioning

confidence: 99%

Section: The Cluster Questionmentioning

confidence: 99%

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Influence of the nematic order on the rheology and conformation of stretched comb-like liquid crystalline polymers

et al. 2000

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Microphase‐Separated Morphology and Liquid Crystal Orientation in Block Copolymers Comprising a Main‐Chain Liquid Crystalline Central Segment Connected to Side‐Chain Liquid Crystalline Segments at Both Ends

Koga

Satō

Kang

et al. 2017

Macro Chemistry & Physics

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The self‐assembly behavior of ABA triblock copolymers comprising side‐chain (SC) liquid crystalline (LC) polymer (A blocks) and a main‐chain (MC) LC polyester (B block) is investigated for SCLC segment volume fractions (ϕ) ranging from 22% to 81%. At ϕ = 81% and 65%, the MCLC segments form cylinders and spheres, respectively, embedded in an SCLC matrix. At ϕ ≤ 56%, block copolymers form lamellar microdomains in which each segment forms smectic layers parallel to the lamellae. Whereas MCLC segments are mostly extended along the lamella normal but are folded to fit within the lamellae, the SCLC segment backbone is more elongated, traversing the smectic layers. Such backbone dimensions and mesogens' orientation in the SCLC segment are explained in light of the small interfacial area with the B5 segment, which is conserved even when the SCLC segment is in the isotropic liquid state.

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Conformation of comb‐like liquid crystal polymers in isotropic solution probed by small‐angle neutron scattering

Zhao¹,

Jamieson²,

Olson³

et al. 2006

J Polym Sci B Polym Phys

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The conformational characteristics of a comb‐like side‐chain liquid crystal polysiloxane (SCLCP), dissolved in deuterated chloroform, were evaluated by small‐angle neutron scattering (SANS) measurements over a wide q range. SANS studies were carried out on specimens with constant backbone length (DP = 198) and variable spacer length (n = 3, 5, and 11), and with constant spacer length (n = 5) and variable DP (45, 72, 127, and 198). The form factor P(q) at high q was analyzed using the wormlike chain model with finite cross‐sectional thickness (Rc) and taking into account the molecular weight polydispersity. The analysis generated values of persistence length in the range lp = 28–32 Å, considerably larger than that of the unsubstituted polysiloxane chain (lp = 5.8 Å), with contour lengths per monomer comparable to the fully‐extended polysiloxane backbone (lm = 2.9 Å). This indicates a relatively rigid SCLCP chain due to the influence of the densely attached mesogenic groups. The SCLCP with n = 11 is more flexible (lp = 28 Å) than those with n = 3 and n = 5 (lp = 32 Å). The cross‐sectional thickness increases with spacer length, Rc ∼ n0.21±0.02 (3 ≤ n ≤ 11), and the contour length per monomer decreases with increasing spacer length, lm ∼ n−0.35±0.01. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2412–2424, 2006

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Effect of the Molecular Weight on the Whole Conformation of a Liquid Crystalline Comb-like Polymer in Its Melt

Cited by 19 publications

References 21 publications

Influence of the nematic order on the rheology and conformation of stretched comb-like liquid crystalline polymers

Influence of the nematic order on the rheology and conformation of stretched comb-like liquid crystalline polymers

Microphase‐Separated Morphology and Liquid Crystal Orientation in Block Copolymers Comprising a Main‐Chain Liquid Crystalline Central Segment Connected to Side‐Chain Liquid Crystalline Segments at Both Ends

Conformation of comb‐like liquid crystal polymers in isotropic solution probed by small‐angle neutron scattering

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